Telephone system



June 11, 1940. R U N $203,756

TELEPHONE SYSTEM Filed Feb. 24. 1938 V v 5 Q I I. Wm-p1 4- c-l a dmk I lfiwn I l y I im WT4.

IN VENTOR. R/CHA RD UREA N ATTORNEY.

Patented June 11,

UNITEDSTATES PATENT OFFICE TELEPHONE SYSTEM Richard Urban, Berlin-Siemensstadt, Germany,

assignor to ,Siemens & Halske Aktiengesellschaft, Wernerwerk, Siemensstadt, near Berlin,

Germany Application February 24, 1938, Serial No. 192,213 In Germany March 8, 1937 i 19 Claims. (Cl. 179-28) {The invention relates to a circuit arrangement 3 mon step-by-step control from the sending stain I are a large number of subscribers, the many partion or, it can be produced by stepping devices individual to the various stations which are mere,

ly set in operation together from the sending station. I i i i In systems employing common step by step control of all the switches from the sending station difficulties are encountered if when; there I allel switches are tobe set with certainty. Thus lit) either large sources of sending currentare necessary (a question of economy) or; very sensitive receiving devices must be provided which are, however, also very prone to faults (a question of efficiency). On the other hand in systemswhere the switchesare only started up in common and are then set synchronously by stepping devices individual to the branch stations, the means for ensuring the synchronous setting, plays an important part. Thus it is difficult for example in systems in which the switches after having been started at each branch station operate under self'interrupter action, in the first place to start up the automatic interrupter circuits at all the branch stations together and then to maintain synchronism between them in all conditions of working (variation of battery potentialaor the like). Similarly in systemsin, which pendulums are used which are released on thecommencement of selection and then oscillate freely, difficulties arise in respect of the equality inlength ofvthe various pendulums. In addition in these systems there also have to be provided the special devices for the satisfactory restoration of the pendulums to the rest position. In systems in which the switches are driven under spring action the time of operation is dependent .upon the actualtension in the spring as is known in all such arrangements. A further important disadvantage resides in that the drive can only be efiective when the springs atall the branch stations are fully wound. I

The invention aims at securing an efficient synchronous operation of the switches at the branch stations of party lines, while using simple devices at the sending and receiving stations and this is achieved while avoiding the disadvantages of the previous solutions in that synchronous motors are provided as the selecting devices at, the branch stations and are fed directly at the branch stations from an alternating current supply which is independent of the party line and is common to all the branch stations. 1 a

The arrangement according to the invention is particularly applicable where there is a common supply of alternating current accessible to all the branch stations so that the synchronous motors can be connected to this common supply in a similar manner to synchronous clocks. On account of the direct feeding from the alternating current supply, the considerable potential losses otherwise occurring when feeding over the party line are avoided. Since the consumption of small synchronous motors is very small, it is economically practical to have the synchronous motors permanently connected and to allow them to operate continually. Moreover,it is possible to providespecial devices as for synchronous clocks which set the motors out of operation in the event of faults in the alternating current supply and also to indicate these faults to the subscriber and to bring the switches to rest in a pre-arranged position.

In systems in which the common supply is liable to be frequently out of order it is more advantageousnot to allow the synchronous motors to run continuously but to connectthem up only on the commencement of a selecting operation. The, synchronous operation of these motors is thensecured in a special manner.

The call sending and call receiving devices are particularly, simple if the synchronous motors are equipped with rotary wipers which connect the ringing current which is connected in preparation to the calling station to the common line of the selection. 1

With party lines it is frequently desired, not only to call individual subscribers of the line, but inspecial cases to call a number or all of the subscribers together (collective call). For this purpose the devices can be so arranged that on a collective call, bells are operatedsimultaneously other stations.

at all the branch stations. Since with this arrangement, however, the distribution of current .over the line is unfavorable, it is preferable to ring the subscribers in succession over the individual calling positions as the rotary wipers roinfluenced in any way by the selecting current passing over the line, filter circuits can be arranged in front of the speaking devices to-block the passage of the selecting current (having the usual mains frequency of 50) to the speaking devices without thereby prejudicing conversation.

l hrthermorablocking means can be provided at the-branch stations which, during a selective operation for example in dependence upon selecting current transmitted over the line, prevent the transmission of further calls on the part of While a call is in progress no blocking means are necessary since secrecy is not provided and the subscribers determine whether the line is free or not by taking up-their receivers and listening.

In thelattached drawings, embodiments of the invention a'reshown to which the invention is not limited, in which Fig. 1 shows a party lineto which a plurality of branch stations can be connected.

Figs. 2 and 3 show modifications thereof.

In Fig.1 there is shown a party line GL to whichany number of branch stations can be connected. Each of these stations is provided with a synchronous motor Dm which is supplied over the transformer Tr from the alternating current network common to all the stations. When these synchronous motors have once been set in synchronism they operate continuouslyin synchronism provided that they are fed from the same network and no faults due to line breakages or the like occur. The synchronous motors are each provided with two wipers dm which passover contacts, of which one is provided as a calling contact and enables a calling circuit to be closed, for example, over a bell Wk, this calling contact being arranged in a difierent position at'each station in the known way. The other contacts traversed by the wiper are connected to corresponding contacts of a second contact bank which are connected bythe wiper of'a dial switch (WT) which is set by hand. In place of this dial switch other selecting devices can be used, for example key sets in which each key is connected to one of the contacts. At each station. a ringing key (RT) is provided which according to its position (tothe left or to the right) determines the type of call (individual call or collective call). The speaking devices (TSt) are connected to the "common line over contacts controlledby the ..no.w, for example, subscriber Tl wishes to call subscriber T4, he tests by way of his telephone to see whether the line is already engaged. If the line .isfree he sets his dial switch WTI with its two wipers a and :b on contact 4 of the wanted subscriber. ,The wipers dmla and dmlb which are rotatingat this time remain ineffectiveuntil the ringing key RT at the calling station is thrown to the left so'that' the following circuit is set up: transformer Trl, ringing key B'Il in, position e, wiperrw of the dial switch WTI on contact 4, wiper dmla on contact 4 and b lead of the common line GL, wiper dm la at the station T4 on contact 4, condenser C4, bell WM, wiper dmlli on'contact 4, a lead of the common line GL, wiper dmlb on contact 4, wiper b of the dial switch WI'l on contact 4, ringing key RTI in position c, transformer Tri. 'I'he selecting current flowing in this circuit operatesthe bell W104 at the wanted station'on every rotation of the wipers (dm) during the time in which. the wipers elm-l and dmfare ion the contact 4 which is constructed asa segment. The, ringing is thus re peated aslong as the ringing key RTI remains depressed. When the wanted subscriber replies conversation can take place. During this time alsothe wipers of the synchronous motors are rotating;

Itis also possible in one're'volution of the wipers of the syhchronous'motors' to call not only one subscriber 'but'any desired number of subscribers. For this, it' is necessary to use key sets or the like as selecting switches which enable a plurality of keys to'be' operated in one selective operation.

In order to prevent during the calling of one branch station further calls proceeding between other stations, busy signals and blocking devices can bearr'ange'd and be fed, for example, by the alternating current transmitted over the common line during calling.

At the end of the call the subscribers hang up their receivers. The system can beso arranged that 'the'selecting switch WT is restored to normal againthrou'gh the replacement of the receiver; the selecting switch can alternatively remain. in'its operatedposition independently of the replacement of the'receiver until the next callis initiated If ac'ollective call (conference call) to all the subscribers is required; theringing switch RT at the calling station has to be displaced to the right into the position g. In this position the ringing circuit does not only pass over one particular contact which is closed 'transitorily on each rotation of the wiper, but the alternating ringing current'is applied permanently to the common line GL. This alternating current then switches o-n'the bells at all the branch stations in succession as soon as the wipers dm pass over the associated contacts. On account of the blocking devices connected in front of the speaking device's, intelligibility is not damaged even when ringing current is being transmitted. To terminate a collective call the ringing switch RTis restored to itsoriginal position.

Inthe arrangement shown in Fig. 2, which, so

farasthe speaking and sendingdevices are concerned, corresponds with Fig. 1, the switches at the stations do not rotatecontinuously but are only connected to the common supply network on the initiation of acall. The construction of the switches as synchronous motors ensuresthe Synchronous operationofwall switchesif these are connected up simultaneously at all the branch stations.

The operation. of the arrangement shown in Fig. 2 is as follows: WIfthe subscriber Tl, for example, wishes to call the subscriber T4,x1then-as in Fig. 1, he

sets the selecting switch. WTI on contact 4. When the ringing switch RTI is brought into position; wiper dmla inthezeroposition, and now. on the one handoverthe start relay RI and wiper dmlc and onthe other hand in parallel therewith over the start relay Rat all the other branch stations (for example R4 and dm4c at the station 4), wiper a'rm'lb, (in the restposition), ringing switch RTI (in the operating position). and back to transformer Trl. In. this circuit the start relays R are operatedat all the branch stations and by way of their contacts (r1; r4, etc.) connect the associated synchroand establish :(dmld, dm4d, etc.) which, for example, are connous motors (Dml, Dm4, etc.) to thencommon network. All the synchronous motors. start up locking circuits .over wipers structed as rotary off-normal contacts, which circuits are independent of the associated relays Ryduring: rotation. .Thestart relays R are disconnected when the synchronous motors are set in'operation and are reconnected after the completion of each rotation. If s then alternating each time the wiper occupies the associated segment. When the called party replies, ringing current is disconnected by throwing over the ringing switch RTI. =The synchronous motors continue, for the time being, and on reaching the zero position, the relays R no longer energize on account of the absence of alternating "ringing current and consequently the synchronous motors are disconnected and remain in the zero position. 1

Ifa collective call (conference call) to be setup, the mode of operation is different from that of the system in Fig. 1. In this case, the

selecting switch and not the ringing switch of the calling station is usedtocharacterize a collective call inthat a calling contact associated with the station itself is used, since that at the calling station is not otherwise required forcalling. Thus, a special switching position of the ringing switch for collectivecalls is avoided. At the calling station Tl, by setting the selecting switch W'Il on contact I (:contact g) a ringuing circuit independent of the wipers dmla and dmlb is prepared over the party line GL. 1 As soon now as the ringing key RTI is operated, alternating current flows permanently over the common line, as in Fig. 1, whereby on every rotation of the synchronous motor the bells at. the .various branch stations are operated suecessively in the same way as has been described in connectionwith Fig. 1.

The system can'alternatively be so arranged that when the selecting switch is set on a special contact for collective calls, the bells at all the branch stations are operated simultaneously to promote a collective call. In this case, it is necessary to feed all the bells simultaneously over i the common line.

1 In systems accordingto Fig. 3, the synchro nous motorsare permanently connected to the station as in Fig; l, but in this case the system is so arranged that the wipers of these switches do not rotate permanently but only during the period of selection so that the contacts traversed by these wipers are only little used. The other devices at the stations are fundamentally the same as inthe arrangements accordingto Figs. 1 and 2.

The mode of operation is as follows:

' If for example subscriber Tl wishes to cal subscriber T4, alternating current is connected to the common lineGL after the selecting switch WTI has been set on contact 4 and after the traverse the start relay RI atthe calling station arranged in bridge across the line, but in addition all the other parallel starting relays at the energizing of the starting relays R, the coupling relays (Kl, K4, etc.) at .all the branch stations, are connected up to the transformers Tr in parallel with the rotary magnet. The coupling magnets couple theywipers (aim-1. 011124, etc.) to the rotary, magnets so that they traverse their associatedrontact. banks synchronously at all the stations. When wiper dmla reaches contact .4 of the wanted party, a circuit is completed for the wanted partys bell .Wk4, in the same manner as already described apropos of Figs. 1 and 2. The: bell W704. operates each time the associated contact is passed, over. When the wanted party replies theringing key RTI at the calling station is restored to normal and disconnects the ringing current. On reaching the zero position, the start relays R can no longer energize, so that the coupling magnets are disconnected. The wipers at all stations are 1 thus brought to rest in the zero position while the synchronous motorsthemselves continue to rotate continuously, under the influence of the alternating current from the supplynetwork. If a collective call is to be set up, the selecting switch WTI is set, on the contact I (:contact g) associated with the calling subscriber, for example Tl. Over this contact, after the ringing key RTI has been operated, alternating current is-permanently connected to the common line, so that the bells at all the branch stations offlthe. common line are operated in succession. If, however, it' is desired to operate the bellsat allithel stations simultaneously for a conference callpa special calling contact for conference callsflfor example, contact 9, must be provided over whichthe' bells at all the stations are operated simultaneously. 1

What isclaimed is: .lfIn combination with a telephone system comprising a party line serving a plurality of stations each having connected .to said line a selecting device, a synchronous motor at each station for driving the selectingdevice at that stabranch stations, for example R4. Through the tion, and an alterna n current netw rk e v ing said stations independentlyoi said telephone for driving the selecting device at that station,

and an alternating current network serving said stations independently of said telephone line for operating said motors in synchron-ism, said mo tors being permanently connected to said network and operating continuously.

3. In a telephone system, a party line serving a plurality of stations, a selecting device ateach of said stations connected to said line, an. alternating current network serving said stations independently of said party line, a synchronous motor at each station operated continuously by current received over said network,an'd means at each stationoperable in one way to mechanically link the motor at that station to the selectingdevice thereat therebyto drive said selecting device and operable in another way to free the motor from the device thereby to permit the device to remain idle. Y c 1 4. In a telephone system, a party line serving a plurality of stations, aselecting device at each of said stations connected to said line, a synchro nous motor at each station for driving the selecting device thereat, anal-ternating current net'- work serving said stations independently of said telephone line, means at'each station for completing an operating circuit from said network to the motor at that station, and means at one of said stations for operating saidlast means atall of said stations simultaneously. I

-5. In combination, an alternating current network, a plurality of synchronous motors operated by current received over said network, a plurality of rotaryswitches driven in synchronism each by one of said motors, a signalling line common to said switches, a signal receiving device associated with each switch, said devices connected to said signalling line in turn by their associated switches, and means for impressing signalling current upon said line continuously thereby to operate said devices one after another.

6. In combination, an alternating current network, a plurality of synchronous motors operated by current'received over said-network, a plurality of rotary switches driven in synchronism each by one of said motors, a signalling line common to said switches, a signal receiving -device associ ated .with'each switch, said devices connected to said signalling line in turn by their associated switches, means operated by current received'over said network for impressing signalling current upon saidline periodically and in synchronism with the connection of a particular device to said line, and variably operable selecting means for synchronizing the application of saidsignal ling current with the connection to said line of I any desired one of said devices.

sired position, and a. plurality of signal receiving devices associated with other ones of said switchea'each of said devices being connectedto the line over the wipers of a particular switch as that switch passes through a particular. position.

'8. In a telephone system, a party line serving a plurality of stations, a multi-position switch at each station, a device at each station connected to the. line by the switch thereat when said switch occupies a particular position, the devices at the different stations being connected to said line in difierent positions of their associated switches, an alternating current network serving said stations inde-' pendently of said party line, and a synchronous motor at'each station operated by current received over said network, said motors driving the switches at said stations in synchronism.

9. In a telephonesystem, a party line serving a plurality of stations, a multi-position switch at each station, a device at each station connected to the line by the switch thereat when said 7,

switch. occupies a particular position, the devices at the different stations being connected to said line in different positions of their associated 1".

switches, an alternating current network serving said stations, a synchronous motor at each station operated continuously by current received from said network, and means at all stations controlledinunison over the party line for mechanically linking the motors at the individual stations to the switches at the corresponding stations,

thereby to initiate operation of said switches simultaneously.

10. Ina telephone system, a party line serving a'plurality of stations, a multi-position switch at'each station, a device at each station connected to the line by the switch thereat when said switch occupies a particular position, the devices at the different stations being connected to said line in different positions of their asssociated switches, an alternating current network serving said stations, a synchronous motor at each station operated by current received over said not- Iworkjsaid motors driving the switches at said synchronous motors at the stations operating over said alternating current network and driving said switches in synchronism, a device-at each station connected to said party line by the switch at that station during a portion of the rotation ofsaid switch, the connection of each device being outof phase with the connection of the other devices, and means at each stationincluding the switch thereat for applying current to the party line concurrently with the connection to ,saidparty line of the device at any desired other station thereby periodically to actuate said device.

12. Ina telephone system, a party lineserving -alplurality of stations, an alternating current network serving said stations independently of said party line, a rotary switch at each station, synchronous motors at the stations operated continuously by current received over said network,

means at all of said stations operated in unison from anyof the stations to' mechanically link the motors at the individual stations to the corresponding switches thereby to drive said switches in synchronism, a deviceat each station connected to said party line by the switch at that station during a portion of the rotation of said switch, the connection of each device being out of phase with the connection of the other devices, and means at each station including the switch thereat for applying current to the party line concurrently with the connection to said party line of the device at any desired other station thereby periodically to actuate said device.

13. In a telephone system, a party line serving a plurality of stations an alternating current network serving said stations independently of said party line, a rotary switch at each station,

synchronous motors at the stations operating over said alternating current network and driving said switches in synchronism, a device at each station connected to said party line by the switch at that station during aportion of the rotation of said switch, the connection of each device being out of phase with the connection of the other devices, a selecting switch at one station, said selecting switch having a plurality of positions each corresponding to one of the other stations and effective when moved to a position correspending to a particular station to cooperate with the rotary switch at said one station to apply current to the party line concurrently with -the connection to said party line of the device at said particular station thereby periodically to actuate said last device.

14. A telephone system as claimed in claim 13, wherein said selecting switch also has a special position and is efiective when moved to said special position to apply current to said party line continuously during one or more revolutions of ,said rotary switches thereby to actuate each device one or more times.

3 15;, In a telephone system, a party line serving a plurality of stations, an alternating current network serving said stations independently of said party line, a rotary switch at each station, synchronous motors at the stations operating over said alternating current network and driving I said switches in synchronism, a ringer at each station connected to said party line by the switch current upon said line continuously during one or more revolutions of said switches thereby to actuate each ringer one or more times.

a 16. A telephone system as claimed in claim 15, wherein said ringing, current is alternating current derived from said network. 17. In a telephone system, a party line serving a plurality of stations, an alternating current network serving said stations independently of said party line, a rotary switch at each station, synchronous motors at the stations operating oversaid alternating current network and driving said switches in synchronism, a ringer at each station connected to said party line by the switch at that station during a portion of each revolution of said switch, the connection of each ringer being out of phase with the connection of the other ringers, and means at each station including the switch thereat for impressing ringing current upon said party line concurrently with the connection to said party line of the ringer at any desired other station thereby periodically to actuate said last ringer.

18. In a telephone system, a party line serving a plurality of stations, an alternating current network serving said stations independently of said party line, a rotary switch'at each station, synchronous motors at the stations operating over said alternating current network and driving said switches in synchronism, a ringer at each station connected tosaid party line by the switch at that station during a portion of each revolution of said switch, the connection of each ringer being out of phase with the connection of the other ringers, and means at each station including the switch thereat for impressing alternating current derived from said network upon said party line concurrently with the connection to said party line of the ringer at any desired other station thereby periodicallyto actuate said last ringer. I

19. In a telephone system, a party line serving a plurality of stations, an alternating current network serving said stations independently of said party line, a rotary switch at each station, synchronous motors at the stations operating over said alternating current network and driving said switches in synchronism, a ringer at each station connected to said party line by the switch at that station during a portion of each revolution of said switch, the connection of each ringer being out of phase with the connection of the other ringers, means for impressing alternating current derived from said network upon said party line to actuate one or more of said ringers, a filter at each station for blocking said derived alternating current, and talking instrumentalities ,at each station connected to the party line 

